Big Brown has Quarter Crack

[miraja2]

I think it depends on what criteria you are looking at when you evaluate whether or not some sire is, or is not, a disappointment.

As a sire of racehorses Secretariat wasn't great, but he was pretty good.
As a sire of sires, he was useless.
As a broodmare sire, he was an absolutely huge success.

People could reasonably make the argument that Secretariat was a great sire by pointing to all of the Storm Cat and AP Indy blood in the breed today. Somebody else could also reasonably argue that no sire that completely failed in establishing a sire line should be called a great sire.
In some respects, both of those people would be right.